Cable skin layer with access sections integrated into a cable jacket

ABSTRACT

An optical fiber cable includes a central tube having a first inner and a first outer surface. The first inner surface defines a bore along a longitudinal axis of the cable. Optical fibers are disposed within the bore of the central tube. A cable jacket is disposed around the central tube. The cable jacket has a second inner and a second outer surface defining a first thickness. A skin layer is disposed around the cable jacket. The skin layer has a third inner and a third outer surface defining a second thickness that is 100 μm or less. The cable jacket material is different from the skin layer material, and the third outer surface defines the outermost surface of the optical fiber cable. Access sections made of the second material extend from the skin layer into the first thickness of the cable jacket.

CROSS-REFERENCED TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 ofU.S. Provisional Application Ser. No. 62/881,298 filed on Jul. 31, 2019,the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

The disclosure relates generally to optical fiber cable constructionsand more particularly to optical fiber cable constructions having a skinlayer to provide a cable jacket having enhanced functionality. Opticalfiber cables have a balance of mechanical properties relating to, interalia, the environment in which they are used, how they are constructed,and how they are installed. Balancing the properties of an optical fibercable often involves a trade-off in desired properties. For example,utilizing a particular material to achieve a desired environmentalproperty may make construction or installation of the cable moredifficult.

SUMMARY

In one aspect, the present disclosure relates to an optical fiber cable.The optical fiber cable includes a central tube having a first innersurface and a first outer surface. The first inner surface defines abore along a longitudinal axis of the optical fiber cable. At least oneoptical fiber is disposed within the bore of the central tube. A cablejacket is disposed around the central tube. The cable jacket is made ofa first material and has a second inner surface and a second outersurface defining a first thickness therebetween. A skin layer isdisposed around the cable jacket and is made of a second material. Theskin layer has a third inner surface and a third outer surface defininga second thickness therebetween. The second thickness is 100 μm or less.The first material is different from the second material, and the thirdouter surface defines the outermost surface of the optical fiber cable.Further, at least one access section made of the second material extendsfrom the skin layer into the first thickness of the cable jacket.

In another aspect, the present disclosure relates to a method of formingan optical fiber cable. In the method, a cable jacket made of a firstmaterial is extruded around a central tube. The central tube has aninterior bore having at least one optical fiber disposed therein. A skinlayer made of a second material is coextruded around the cable jacket.The second material is different from the first material, and the skinlayer has a thickness of 100 μm or less. At least one split in the cablejacket is created with an extrusion die so that the second materialflows into the at least one split to form at least one access section inthe cable jacket.

In still another aspect, the present disclosure relates to an opticalfiber cable. The optical fiber cable includes a central tube having afirst inner surface and a first outer surface. The first inner surfacedefines a bore along a longitudinal axis of the optical fiber cable. Atleast one optical fiber is disposed within the bore of the central tube.A cable jacket is disposed around the central tube. The cable jacket ismade of a first material and has a second inner surface and a secondouter surface defining a first thickness therebetween. A skin layer isdisposed around the cable jacket. The skin layer is made of a secondmaterial and has a third inner surface and a third outer surfacedefining a second thickness therebetween. The second thickness is 100 μmor less. The first material has a first coefficient of friction and afirst coefficient of thermal expansion (CTE). The second material has asecond coefficient of friction and a second CTE. The second coefficientof friction is less than the first coefficient of friction and the firstCTE is less than the second CTE.

Additional features and advantages will be set forth in the detaileddescription that follows, and in part will be readily apparent to thoseskilled in the art from the description or recognized by practicing theembodiments as described in the written description and claims hereof,as well as the appended drawing.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understand the natureand character of the claims.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing is included to provide a further understandingand are incorporated in and constitute a part of this specification. Thedrawing illustrates one or more embodiment(s), and together with thedescription serves to explain principles and the operation of thevarious embodiments.

FIG. 1 depicts a longitudinal cross-sectional view of an optical fibercable having a skin layer, according to an exemplary embodiment.

FIG. 2 is a graph of the coefficient of friction (CoF) of exemplaryembodiments having a skin layer and comparative examples.

FIG. 3 depicts an embodiment of an optical fiber cable having a skinlayer with access sections extending into the cable jacket, according toan exemplary embodiment.

FIG. 4 depicts an embodiment of an optical fiber cable having a skinlayer and support ribs, according to an exemplary embodiment.

FIGS. 5A and 5B depict embodiments of a cable extrusion die for creatingaccess sections in the cable jacket, according to an exemplaryembodiment.

FIG. 6 depicts an embodiment of an optical fiber drop cable in which theoptical fibers are contained within a wrapped armor layer surrounded bya cable jacket, according to an exemplary embodiment.

FIG. 7 depicts a flowchart for a method of preparing the optical fiberdrop cable of FIG. 6, according to an exemplary embodiment.

DETAILED DESCRIPTION

Various embodiments of an optical fiber cable having a skin layer arounda cable jacket are provided. As will be discussed more fully below, theskin layer enhances a desired property of the cable jacket. For example,the cable jacket may desirably have a low coefficient of thermalexpansion but a higher than desired coefficient of friction. Thus,according to the present disclosure, the skin layer is provided aroundthe cable jacket to enhance the property of the coefficient of friction,particularly to lower the coefficient of friction, without substantiallydiminishing the desired property of the low coefficient of thermalexpansion. Other combinations of properties for the cable jacket andskin layer are discussed below. Further, in embodiments, the skin layeris coextruded with the cable jacket, and during coextrusion, accesssections are formed that extend into or through the thickness of thecable jacket to provide access to the interior of the cable jacket. Alsodisclosed herein are embodiments of an optical fiber drop cable in whichthe optical fibers are contained in a metal tape instead of a centraltube or buffer tube. A cable jacket is formed around the metal tape soas to provide a simplified, non-preferential bend drop cable. These andother aspects and advantages will be discussed in relation to theexemplary embodiments disclosed herein. These embodiments of the opticalfiber cable disclosed herein are provided by way of example and not byway of limitation.

FIG. 1 depicts an embodiment of an optical fiber cable 10 having a skinlayer 12 according to the present disclosure. The optical fiber cable 10includes a plurality of optical fibers 14 contained within a centraltube 16 in a loose tube configuration. The central tube 16 has a firstinner surface 18 and a first outer surface 20. The first inner surface18 defines a central bore 22 in which the optical fibers 14 aredisposed. In embodiments, the central tube 16 includes from one totwelve optical fibers 14 within the central bore 22. The central bore 22may also contain water-blocking material, such as gels, yarns, powders,or tapes. The central tube 16 has a first thickness T₁ between the firstinner surface 18 and the first outer surface 20. In embodiments, thefirst thickness T₁ is from 0.30 mm to 0.50 mm, more particularly from0.35 mm to 0.45 mm. In embodiments, the first outer surface 20 defines adiameter of from 2.5 mm to 3.5 mm. In embodiments, the central tube 16is made from polybutylene terephthalate (PBT), polyester, or anothersimilar material.

On the first outer surface 20 of the central tube 16, a plurality ofstrengthening yarns 24 are provided. As can be seen in the embodiment ofFIG. 1, the strengthening yarns 24 are arranged in diametrically opposedstrands 26. In embodiments, each strand 26 includes from one to eightstrengthening yarns 24, more particularly four strengthening yarns 24.Further, in embodiments, the strengthening yarns 24 include at least oneof aramid fibers, glass fibers, or basalt fibers. In embodiments, thestrengthening yarns 24 having a linear density of 1000 denier to 2000denier, more particularly a linear density of 1400 denier to 1500denier. In embodiments, the strands 26 of strengthening yarns 24 runstraight and longitudinally along the length of the central tube 16. Inother embodiments, the strands 26 of strengthening yarns 24 arehelically wrapped around the central tube 16.

Surrounding the strengthening yarns 24 is a cable jacket 28. The cablejacket 28 has a second inner surface 30 and a second outer surface 32.The second inner surface 30 contacts the strengthening yarns 24 and, inregions, the first outer surface 20 of the central tube 16. In theregion where the second inner surface 30 contacts the central tube 16,the cable jacket 28 has a second thickness T₂ between the second innersurface 30 and the second outer surface 32 of from 0.3 mm to 0.85 mm,more particularly from 0.45 mm to 0.7 mm. The skin layer 12 is disposedaround the cable jacket 28. In particular, the skin layer has a thirdinner surface 34 and a third outer surface 36. In embodiments, the thirdouter surface 36 defines the outermost surface of the optical fibercable 10 and defines an outer diameter of the optical fiber cable 10 offrom 3.75 mm to 5.0 mm. Further, the third inner surface 34 contacts thesecond outer surface 32 of the cable jacket 28. In embodiments, the skinlayer 12 has a third thickness T₃ of less than 100 μm, more particularlyfrom 30 μm to 70 μm.

In embodiments, the skin layer 12 is selected to provide a newfunctionality and/or to enhance a property of the cable jacket 28. Forexample, the cable jacket 28 may be selected for a particularly desiredfirst property at the expense of (or at least without specificconsideration to) another desired second property. The skin layer 12 canaddress the deficiency in the second property so that the optical fibercable 10 can take advantage of both the first and second properties. Inone embodiment, the cable jacket 28 is selected to provide a lowcoefficient of thermal expansion (CTE), which provides desirableantibuckling properties. However, in certain circumstances, the low CTEmaterial may also have a relatively high coefficient of friction, whichcan create difficulty during stranding of optical fiber cables and ininstalling the optical fiber cables through ducts. Accordingly, in anembodiment, the low CTE cable jacket 28 is provided with a skin layer 12of a material having a low coefficient of friction. In this way, theoptical fiber cables 10 are able to have both desired properties, namelyantibuckling provided by the cable jacket 28 and low coefficient offriction provided by the skin layer 12.

In embodiments, the low CTE cable jacket 28 comprises a material thatcontains from 30% to 60% by weight of one or more polyolefins, from 30%to 60% by weight of one or more thermoplastic elastomers, and up to 20%by weight of one or more inorganic fillers wherein the materialcomprises a coefficient of thermal expansion of 160(10⁻⁶) m/mK or less.Exemplary polyolefins suitable for use in the low CTE cable jacket 28include one or more of medium-density polyethylene (HDPE), high-densitypolyethylene (HDPE), low-density polyethylene (LDPE), linear low-densitypolyethylene (LLDPE), and/or polypropylene (PP), amongst others.Exemplary thermoplastic elastomers suitable for use in the low CTE cablejacket 28 include one or more of ethylene-propylene rubber (EPR),ethylene-propylene-diene rubber (EPDM), ethylene-octene (EO),ethylene-hexene (EH), ethylene-butene (EB), ethylene-vinyl acetate(EVA), and/or styrene-ethylene-butadiene-styrene (SEBS), amongst others.In embodiments, the inorganic fillers have high aspect ratio and areeither rod-like or plate-like. A rod-like filler includes particlesthat, on average, are longer than they are thick. In a particularembodiment, the rod-like filler particles have, on average, a length tothickness ratio of at least 5:1. In an embodiment, the rod-like fillerincludes one or more of wood flour, glass fiber, halloysite,wollastonite, magnesium oxysulfate, and/or other reinforced fibers,amongst others. A plate-like filler includes particles that, on average,are both longer and wider than they are thick. In a particularembodiment, the plate-like filler particles have, on average a length tothickness and a width to thickness of at least 5:1. In an embodiment,the plate-like filler includes one or more of mica, talc,montmorillonite, kaolinite, bentonite, synthetic clay, and/or otherclays, amongst others.

The composition of the low CTE cable jacket 28 can further includedispersants and/or compatibilizers. Such additives aid fillerdispersion, improve compatibilities between polymer matrices, andstabilize the phase morphology. Exemplary compatibilizers include blockcopolymers that have alternating olefin block and one or more othermonomer blocks, i.e., alternating block of polyethylene and styrenecontaining segment (compatible with SEBS). Exemplary compatibilizersalso include a grafted polymer having a polyolefin backbone that isgrafted with a monomer that is compatible with the used thermoplasticelastomer. In an embodiment, carbon black is added to the composition,which absorbs ultra-violet light for outdoor applications. Theadditives, such as dispersants, compatibilizers, carbon black, etc. maybe present in the low CTE cable jacket 28 in an amount of up to 5% byweight.

In embodiments, the skin layer 12 comprises a material having a lowcoefficient of friction, e.g., a coefficient of friction of 0.30 orless, more particularly 0.25 or less, and most particularly 0.20 orless. In embodiments, the skin layer 12 comprises high densitypolyethylene (HDPE), medium density polyethylene (MDPE), low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), ultra highmolecular weight polyethylene (UHMWPE), very low density polyethylene(VLDPE), polyamide (e.g., nylon 6, 6/6, 12), polyester, or polyolefingrafted polyamide-6 (PO-g-PA6; e.g., Apolyha® LP21H available fromArkema, Colombes Cedex, France).

FIG. 2 depicts a graph of the coefficient of friction (CoF) for cables(E1 and E2) having a low CTE cable jacket 28 and a low coefficient offriction skin layer 12 as compared to a cable (CE1) with an MDPE jacketand a cable (CE2) just having a low CTE cable jacket (with no skinlayers). The coefficients of friction for each cable were determinedaccording to IEC TR62470. The box plot of FIG. 2 shows CoF values foreach cable in an initial test and CoF values for each cable in a repeattest. As can be seen, CE1, having just an MDPE jacket and no skin layer,has a relatively low coefficient of friction of around 0.2. CE2, whichjust had a low CTE jacket and no skin layer, had a coefficient offriction of around 0.55-0.60. E1 has a cable jacket 28 comprised of afirst material which is the low CTE cable jacket 28 and has a skin layer12 comprised of a second material including PO-g-PA6 having a lowercoefficient of friction than the first material. E2 has a cable jacket28 comprised of a first material which is the low CTE cable jacket 28and has a skin layer 12 of a second material such as HDPE with a lowercoefficient of friction than the first material. The skin layers 12 forE1 and E2 each may have a thickness of about 50 μm. E1 and E2 each had acoefficient of friction of less than 0.3, and were both about 0.21 orless. Thus, using a thin skin layer 12, a low coefficient of frictioncable can be provided that also has the advantages provided by a low CTEcable jacket 28. Additionally, the cable of E2 also provides improvedimpact resistance, in particular being able to withstand two impacts perlocation at 2.94 Nm impact energy according to ICEA-640.

While the properties of low CTE cable jacket 28 and low coefficient offriction skin layer 12 were described, other combinations of propertiesare also possible. For example, in embodiments, the optical fiber cable10 has a cable jacket 28 comprising polyvinylchloride (PVC). The PVCcable jacket 28 provides cost-effective flame retardance for cables usedboth indoors and outdoors. However, in some circumstances, the PVC cablejacket 28 does not pass the cold impact testing per ICEA-640. In suchcircumstances, the PVC cable jacket 28 may be provided with a skin layer12 of polyvinylidene fluoride (PVDF), which helps the optical fibercable 10 pass the cold impact testing while also improving flameretardant performance. In particular, the cable 10 having the PVC cablejacket 28 and PVDF skin layer 12 has improved crush and impactperformance and an improvement in burn testing.

In still another embodiment, the skin layer 12 is used to facilitateconnectorizing a cable. In particular, certain connectors use heatshrink materials, such as cross-linked polyolefins including having anadhesive layer of ethylene vinyl acetate (EVA) or polyamide-modifiedEVA, to prevent water ingress at the connection. In certaincircumstances, the cable jacket 28 is made from a material, such as PVCor polyethylene, that includes plasticizers that prevents a stable bondto the heat shrink material, or the material from which the cable jacket28 is made may not be compatible with the heat shrink material. In suchembodiments, the skin layer 12 (such as a PO-g-PA6) can be used toprovide a layer compatible with the cable jacket 28 and heat shrinkmaterial or that prevents migration of plasticizers that would renderthe bond unstable.

The skin layer 12 can also be co-extruded with the cable jacket 28 in amanner that provides the optical fiber cable 10 with a fast accessfeature. FIG. 3 is a photograph of an optical fiber cable 10 having askin layer 12 with access sections 38 that extend into the cable jacket28. In the embodiment shown in FIG. 3, the access sections 38 are formedduring coextrusion of the skin layer 12 with the cable jacket 28. Inparticular, a flow splitter is used during extrusion to create adiscontinuity in the extruded cable jacket 28, which is filled with thematerial of the skin layer 12. In the embodiment shown in FIG. 3, theaccess section 38 extends substantially through the second thickness T₂of the cable jacket 28. In embodiments, the access section 38 extendsthrough at least 50% of second thickness T₂ of the cable jacket 28. Inother embodiments, the access section 38 extends through at least 80% ofsecond thickness T₂ of the cable jacket 28. Further, two,diametrically-opposed access sections 38 are shown in FIG. 3, but inother embodiments, the optical fiber cable 10 can include a singleaccess section 38 or a plurality of access sections 38, including asmany as four access sections 38. When there is a plurality of accesssections, each one of the access sections 38 may be generally spacedequidistantly apart around the circumference of the cable 28.

FIG. 4 depicts an embodiment of an optical fiber cable 10 including fouraccess sections 38. Further, as compared to the embodiment of FIG. 3,the access sections 38 of FIG. 4 are wider and, besides providing accessto the interior of the optical fiber cable 10, the access sections 38also act as support ribs that provide, e.g., additional crush resistanceand/or antibuckling properties at cold temperatures. In embodiments, thewidth W of the access sections 38 (as measured at their narrowest point)is from 0.1 mm to 0.3 mm. Further, in embodiments, the access sections38 contain additional fillers and/or low CTE material to enhance thesupport rib function.

Embodiments of the optical fiber cable 10 as described above can beformed via a coextrusion process in which the central tube 16 containingthe plurality of optical fibers 14 is coated with the cable jacket 28.During extrusion of the cable jacket 28, the skin layer 12 is coextrudedaround the cable jacket 28. In order to form the access sections 38, anextrusion die 40 as shown in FIGS. 5A-5B is used. As shown in FIG. 5A,the extrusion die 40 includes a flow splitter feature 42. By increasingthe depth, width, and angle of the flow splitter feature 42, the amountof material deposited in the access sections 38 can be adjusted, e.g.,to form the support ribs shown in FIG. 4. The material of the skin layer12 flows through a first channel portion 44, through second channelportions 46 and over the flow splitter feature 42. The material flowingover the flow splitter feature 42 forms the access sections 38, and thematerial flowing over the second channel portions 46 forms the skinlayer 12.

FIG. 5B depicts a cross-section of the extrusion die 40 of FIG. 5A takenalong line A-A. The extrusion die 40 has a central bore 48 along alongitudinal axis of the extrusion die 40. The central tube 16 havingstrands 26 of strengthening yarns 24 extending alongside the centraltube 16 and having molten cable jacket 28 material extruded thereon ispulled through the extrusion die 40 where the skin layer 12 is appliedover the cable jacket 28, also forming the access sections 38. In thisway, an optical fiber cable 10 having access sections 38 and a skinlayer 12 is formed. As discussed above, the optical fiber cable 10exhibits the beneficial properties of both the cable jacket 28 and theskin layer 12.

In another aspect of the present disclosure, embodiments of an opticalfiber drop cable 100 are provided. The optical fiber drop cable 100includes a plurality of optical fibers 102 disposed within a centralbore 104 formed by an armor tape 106, e.g., steel tape. In particular, aflat (i.e., non-corrugated) armor tape 106 is formed around a bundle ofoptical fibers 102. In embodiments, the bundle of optical fibers 102 mayalso include water-blocking yarns to prevent water from propagatingwithin the central bore 104 formed by the armor tape 106. Surroundingthe armor tape 106 is a cable jacket 108. The cable jacket 108 has aninterior surface 110 and an exterior surface 112. The interior surface110 is in contact with the armor tape 106, and the exterior surface 112defines the outermost surface of the optical fiber drop cable 100. Inembodiments, the exterior surface 112 defines an outer diameter of theoptical fiber drop cable 100 of from 4.0 mm to 5.5 mm, e.g., about 4.8mm.

In embodiments, the optical fibers 102 are bare fibers comprising acore, cladding, coating, and optionally a pigment or ink layer foridentification. Further, in embodiments, the armor tape 106 has athickness of from 0.1 mm to 0.2 mm, and in embodiments, the armor tape106 is made from at least one of steel or aluminum. In embodiments, whenwrapped around the bundle of optical fibers 102 and water-blocking yarn(if provided) the armor tape 106 has a diameter of from 1 mm to 3 mm. Inembodiments, the cable jacket 108 is made from at least one of mediumdensity polyethylene (MDPE), high-density polyethylene (HDPE),low-density polyethylene (LDPE), linear low-density polyethylene(LLDPE), very low density polyethylene (VLDPE), polypropylene (PP),ethylene vinyl acetate (EVA), ethylene-acrylate copolymers, polyolefinelastomer copolymer, polyethylene-polypropylene copolymer, butene- andoctene-branched copolymers, or maleic anhydride-grafted versions of theforegoing polymers.

FIG. 7 provides a flow diagram of a method 200 of forming the opticalfiber drop cable 100. In a first step 202 of the method 200, a bundle ofoptical fibers 102 are provided along with any water blocking yarns thatare to be incorporated into the optical fiber drop cable 100. Inembodiments, the optical fibers 102 are color-coded for identificationpurposes. In embodiments, the bundle includes from one to twelve opticalfibers 102.

In a next step 204, an armor tape 106 (e.g., steel tape) is wrappedaround the bundle of optical fibers 102 and water-blocking yarns. Asmentioned above, the armor tape 106 is flat and not corrugated. In anembodiment, the longitudinal edges of the armor tape 106 overlap by,e.g., 0.1 mm to 0.5 mm once wrapped around the bundle of optical fibers102.

After the armor tape 106 is wrapped around the bundle of optical fibers102, the cable jacket 108 is extruded over the armor tape 106 in a finalstep 206.

Advantageously, the cable constructed according to the embodiment shownin FIG. 6 via the method of FIG. 7 does not include any buffer tubes orstrengthening rods, which creates a drop cable 100 having a relativelysmall diameter and without having a preferential bend direction. Bycomparison, some conventional cable designs include multipleglass-reinforced plastic rods that create a preferential bending axis,making routing the drop cable through ducts with turns in multipledirection difficult. Further, as compared to traditional loose tube andcentral tube cables, the optical fiber drop cable 100 contains lesslayers of material, which reduces the overall size of the cable.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is in no way intendedthat any particular order be inferred. In addition, as used herein, thearticle “a” is intended to include one or more than one component orelement, and is not intended to be construed as meaning only one.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the disclosed embodiments. Since modifications,combinations, sub-combinations and variations of the disclosedembodiments incorporating the spirit and substance of the embodimentsmay occur to persons skilled in the art, the disclosed embodimentsshould be construed to include everything within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An optical fiber cable, comprising: a centraltube having a first inner surface and a first outer surface, wherein thefirst inner surface defines a bore along a longitudinal axis of theoptical fiber cable; at least one optical fiber disposed within the boreof the central tube; a cable jacket disposed around the central tube,the cable jacket comprising a first material and having a second innersurface and a second outer surface defining a first thicknesstherebetween; a skin layer disposed around the cable jacket, the skinlayer comprising a second material and having a third inner surface anda third outer surface defining a second thickness therebetween, thesecond thickness being 100 μm or less; wherein the first material isdifferent from the second material; wherein the third outer surfacedefines an outermost surface of the optical fiber cable; wherein atleast one access section comprising the second material extends from theskin layer into the first thickness of the cable jacket.
 2. The opticalfiber cable of claim 1, wherein the first material has a firstcoefficient of friction and the second material has a second coefficientof friction, and wherein the second coefficient of friction is less thanthe first coefficient of friction.
 3. The optical fiber cable of claim2, wherein the second coefficient of friction is 0.30 or less.
 4. Theoptical fiber cable of claim 2, wherein the first material comprisesfrom 30% to 60% by weight of one or more polyolefins, from 30% to 60% byweight of one or more thermoplastic elastomers, and up to 20% by weightof one or more inorganic fillers and wherein the first materialcomprises a coefficient of thermal expansion of 160(10⁻⁶) m/mK or less.5. The optical fiber cable of claim 4, wherein the skin layer comprisesat least one of high density polyethylene (HDPE), medium densitypolyethylene (MDPE), low density polyethylene (LDPE), very low densitypolyethylene (VLDPE), linear low density polyethylene (LLDPE), ultrahigh molecular weight polyethylene (UHMWPE), a polyamide, a polyester,or a polyolefin grafted polyamide-6.
 6. The optical fiber cable of claim1, wherein the cable jacket comprises polyvinyl chloride and the skinlayer comprises polyvinylidene fluoride.
 7. The optical fiber cable ofclaim 1, wherein the at least one access section extends through atleast 80% of a thickness of the cable jacket.
 8. The optical fiber cableof claim 1, wherein the at least one access section has a narrowestwidth of from 0.1 mm to 0.3 mm.
 9. The optical fiber cable of claim 1,comprising at least two access sections, wherein the at least two accesssections are equidistantly spaced around the cable jacket.
 10. Theoptical fiber cable of claim 1, wherein the second thickness of the skinlayer is 50 μm or less.
 11. A method of forming an optical fiber cable,comprising: extruding a cable jacket comprising a first material arounda central tube, wherein the central tube comprises an interior borehaving at least one optical fiber disposed therein; coextruding a skinlayer comprising a second material around the cable jacket, wherein thesecond material is different from the first material and wherein theskin layer has a thickness of 100 μm or less; and creating at least onesplit in the cable jacket with an extrusion die so that the secondmaterial flows into the at least one split to form at least one accesssection in the cable jacket.
 12. The method of claim 11, wherein thefirst material has a first coefficient of friction and the secondmaterial has a second coefficient of friction and wherein the secondcoefficient of friction is less than the first coefficient of friction.13. The method of claim 12, wherein the second coefficient of frictionis 0.30 or less.
 14. The method of claim 12, wherein the first materialcomprises from 30% to 60% by weight of one or more polyolefins, from 30%to 60% by weight of one or more thermoplastic elastomers, and up to 20%by weight of one or more inorganic fillers and wherein the firstmaterial comprises a coefficient of thermal expansion of 160(10⁻⁶) m/mKor less.
 15. The method of claim 11, wherein the cable jacket comprisespolyvinyl chloride and the skin layer comprises polyvinylidene fluoride.16. The method of claim 11, wherein the skin layer has the secondthickness of 50 μm or less.